I have been staying on SWX2015 because I saw early on a problem with the UI icon mess at the 2016 rollout presentations. There are plenty of things in 2016 I'd like to use, but before I made that leap I read the discussions on this forum. They confirmed my objection to the UI (it wasn't just me that hated it) and the pro's of 2016 were not enough to outweigh the con's of this UI mess. Now it appears (pardon the pun) that the UI issue, though not fully resolved, is at least mostly back to an acceptable classic look.
So my question is posed to those of you that have used or are using SP4.0; do you have any regrets?
Thanks in advance for your feedback.